Abstract
In order to elucidate factors controlling REE concentrations in deep-sea sediments from central to western Pacific, 64 samples were analyzed for major elements by XRF and rare earth elements (REEs) by ICP-MS. Statistical factor analyses were applied for the estimation of factors. The main conclusions are as follows;1) REEs, except for Ce, show remarkably good positive correlation with P2O5, which also correlates with CaO. Further in P2O5-CaO diagram, many samples are plotted near a line with a slope similar to CaO/P2O5 ratio of apatite. These facts indicate that REEs are concentrated in apatite of Pacific sediments. Statistical factor analysis suggests that apatite is the principal factor controlling REE concentrations in the Pacific sediments.2) Many researchers pointed out that airborne transport of continental materials such as loess is also important in controlling the chemistry of marine sediments in addition to the apatite. Based on REE compositions of "loess" and "calculated apatite", other factors controlling REE composition of Pacific sediments were estimated by the factor analysis. Newly identified REE pattern normalized to NASC exhibits a convexity with a peak at Eu, resembling remarkably that of diagenetic Mn nodule. No clear relationship, however, could be established between the third factor and Mn contents of samples.3) The distribution of factor scores revealed that material of loess origin contribute to the sediments mainly of northern Philippine Sea and central Pacific, apatite to those of equatorial Pacific, and the third factor to those in the vicinity of Hawaii islands and northern of Pacific.The result obtained from this study may give us a clue in clarifying the depositional environment of subduction complex on land.
